A Thermodynamic Model for Gas Adsorption Isotherms

A cryosampling system together with a low temperature GC-ICP-MS method have been developed for the determination of phosphine for industrial hygiene purposes. The effect of sampling temperature on the collection efficiency of PH 3 was investigated. Two trapping mechanisms were differentiated for temperature ranges from 2190 to 2160 uC and from 2110 to 235 uC. A cartridge filled with NaOH was used during the analytical desorption step to separate CO 2 from phosphine. Phosphine recovery was found to be better than 98% with peak area and retention times RSD values better than 4% and 2%, respectively. The use of a Nafion 1 drying membrane before cryogenic trapping induced losses of PH 3 of about 15%. Sample conservation in a cryocontainer at 2190 uC over a period of 15 days did not lead to significant losses of PH 3 . For field experiments, air samples were collected in the fumigation room of a tobacco factory after fumigation, and outside the fumigation room during fumigation, using both cryogenic sampling and standard filters impregnated with silver nitrate. The results showed that phosphine concentrations in the tobacco factory were below the limit values for occupational exposure to phosphine (VME (France) and TLV-TWA (USA)) and also below the detection limit of the silver impregnated filter-ICP-AES method. Cryogenic trapping in combination with GC-ICP-MS allowed us to determine phosphine concentrations. The concentrations in ambient air are estimated to be about 1 ng m 23 and the detected concentrations in the vicinity of the fumigation room during the fumigation process are lower than 10 ng m 23 . PH 3 in air reacts with HOx radicals and is removed by this mechanism with a half time of 5-28 hours, depending on the conditions. 1 The sunshine increases the OHx radicals concentration and may reduce the half-life to less than 5 hours. The following reaction of phosphine with OHx may occur:This reaction is dependant on PH 3 concentration and is very rapid, with a reaction rate constant at room temperature of about 1.5 6 10 211 cm 3 mol 21 s 21 . 9 The final product of the

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“…4B). So, the trapping mechanism of phosphine at 2100 uC should follow a Langmuir isotherm as given by the following equation: 25 h~P PzP 0 (T)…”

Section: Resultsmentioning

confidence: 99%

Phosphine emission measurements from a tobacco factory using cryogenic sampling and GC-ICP-MS analysis

Pavageau

Pécheyran

Demange

et al. 2003

J. Anal. At. Spectrom.

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“…However, newer studies based on the SLD model generally consider a slit geometry for the porous material [7][8][9]. In this case, as illustrated in Fig.…”

Section: Sld Modelmentioning

confidence: 99%

“…There are a wide range of theoretical approaches for modeling gas adsorption, from simple empirical fits (e.g., Freundlich isotherms [4]) to strong molecular theories based on molecular dynamics and Monte Carlo simulations. The thermodynamics of adsorption phenomena have been discussed in detail in previous studies [5][6][7]. There are different theories for this purpose, such as the Gibbs isotherm, the treatment of Myers and Prausnitz, vacancy solution theory, Dubinin-Polanyi theory [5], density functional theory [6], and activity-coefficient-based models [7].…”

Section: Introductionmentioning

confidence: 99%

“…The thermodynamics of adsorption phenomena have been discussed in detail in previous studies [5][6][7]. There are different theories for this purpose, such as the Gibbs isotherm, the treatment of Myers and Prausnitz, vacancy solution theory, Dubinin-Polanyi theory [5], density functional theory [6], and activity-coefficient-based models [7]. The simplified local density (SLD) model is a mean-field model that superimposes the fluid-solid (fs) potential on a fluid equation of state (EOS) [8].…”

Section: Introductionmentioning

confidence: 99%

“…Both parts can play an important role in the ability of the model. In all previous studies [4][5][6][7][8][9][10], the Lennard-Jones potential function has been utilized. In this study, we have tried to test the capabilities of another potential function.…”

Section: Introductionmentioning

confidence: 99%

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A New Simplified Local Density Model for Adsorption of Pure Gases and Binary Mixtures

et al. 2010

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Adsorption modeling is an important tool for process simulation and design. Many theoretical models have been developed to describe adsorption data for pure and multicomponent gases. The simplified local density (SLD) approach is a thermodynamic model that can be used with any equation of state and offers some predictive capability with adjustable parameters for modeling of slit-shaped pores. In previous studies, the SLD model has been utilized with the Lennard-Jones potential function for modeling of fluid-solid interactions. In this article, we have focused on application of the Sutherland potential function in an SLD-Peng-Robinson model. The advantages and disadvantages of using the new potential function for adsorption of methane, ethane, carbon dioxide, nitrogen, and three binary mixtures on two types of activated carbon are illustrated. The results have been compared with previous models. It is shown that the new SLD model can correlate adsorption data for different pressures and temperatures with minimum error.

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Non-Arrhenius form of the Henry adsorption on inhomogeneous substrates: the effect of frozen disorder

2017

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A Thermodynamic Model for Gas Adsorption Isotherms

Cited by 15 publications

References 15 publications

Phosphine emission measurements from a tobacco factory using cryogenic sampling and GC-ICP-MS analysis

Phosphine emission measurements from a tobacco factory using cryogenic sampling and GC-ICP-MS analysis

A New Simplified Local Density Model for Adsorption of Pure Gases and Binary Mixtures

Non-Arrhenius form of the Henry adsorption on inhomogeneous substrates: the effect of frozen disorder

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